I have lost Valentine, my synth. When I picked up the super mutant, Strong, I sent him to the Red Rocket. Now I don't know whether I made a mistake or there's a bug, but he never arrived. Is there a way to either recall or track him?

What's the next main quest mission you have? If it is Dangerous Minds then Nick is at a place in the settlement called Goodneighbor, I had this issue my first PT where I got a new companion and I thought I sent him to Sanctuary but couldn't find him, he was in Goodneighbor for the next story mission.